The disclosure relates to propulsion units for propulsion and maneuvering of a vessel provided with an exchangeable sectioned leading edge on the inlet of the nozzle.
There are known propulsion units including a propeller section which is fixed in a surrounding rotor part, in the periphery of which there are arranged permanent magnets or windings for providing magnetic field. The rotor part constitutes the rotor of an electrical motor and is positioned inside a surrounding stator part, which stator part is provided with magnetic devices or windings for generating magnetic field for causing rotation of the propeller section.
U.S. Pat. No. 5,220,231 discloses such a propulsion unit for a seagoing vessel. The propulsion unit has a centrally supported propeller section having propeller blades extending radially between a central part and a radially exterior positioned ring which rotates with a small radial distance from the stator part.
It is an increasing focus on reducing the power requirement for the use of all types of propulsion units for propulsion and maneuvering of a vessel. There are increasing demands for emission of environmentally unfriendly gases and the fuel costs are increasing, something which have resulted in increased focus on development of new solutions, among others, optimization of propeller blades and development of hybrid systems for propulsion of the vessels.
Propulsion units are further provided with a leading edge on the inlet of the nozzle to provide it with a hydrodynamic design. Presently, the most propulsion units being produced and used are provided with a leading edge being integrated in the nozzle itself. This makes the nozzle unnecessary heavy, and the hydrodynamic design is permanent and cannot be changed. This results in that all propulsion units must be custom-made to the actual vessel they are to be used on, and it results in more expensive production of the propulsion units.
In GB1472544 it is disclosed a solution where both the leading edge and the following edge are exchangeable or controllable. The leading edge can be sectioned along the circumference and shaped of a different material than the main part of the nozzle, such as plastics or glass fibers. Disadvantages with this publication are, among others, that the leading edge and following edge are arranged to be fixed in the extension of the nozzle itself, which nozzle then must exhibit an open end on each side. This results in that the leading or following edge must either be welded or it must be fixed both from the inside and outside of the nozzle. By that the leading and following edges must be arranged in the extension of the nozzle like this, this result in that nozzles cannot be mass-produced, but must be custom-made to the individual vessel. Further, by that the leading and following edges are arranged in the extension of the nozzle, this will result in that there is a danger for leakage into the nozzle, especially if the leading or following edge is made of plastics or glass fibers. Further, if the leading and following edges are adjustable, this will be a disadvantage, especially as the adjustment means for this (holes and screws) could result in that the leading or following edge changes design after some time of use, so that the propulsion unit exhibits a different profile than originally intended. This can then result in unfavorable operating conditions for the propulsion unit. It is further not indicated any type of propulsion unit this solution can be utilized on, as it will be a central point how e.g. the propulsion unit is to be arranged to the vessel and how the propeller section is designed.
It is also an increasing focus on providing propulsion units having lower weight, are more rapid and simple to handle under production, and cheaper in relation to prior art solutions. Even though the propulsion unit should have lower weight it is important that it exhibits sufficient strength.